An example of a prior art single package urethane rein composition is a moisture-curable coating-type waterproofing agent, wherein a urethane prepolymer having a terminal isocyanate (NCO) group is mixed with an inorganic filler, as disclosed in Japanese Provisional Patent Publication No. SHO-57-94056, referred to hereinafter as "Prior Art I." In the case of Prior Art I, the NCO group can react with moisture in the air or in the substrate to generate carbon dioxide. The generation of carbon dioxide can cause "blisters", especially when the film coating is thick.
Japanese Patent Publication No. SHO-48-20639 (referred to hereinafter as "Prior Art II") and Japanese Provisional Patent Publication No. HEI-2-55715 (referred to hereinafter as "Prior Art III") disclose oxazolidine-isocyanate compositions. The compositions disclosed in Prior Art II and Prior Art III do not generate carbon dioxide during curing. However, when an oxazolidine-isocyanate composition is mixed with an inorganic filler and stored for a long period, the inorganic filler separates from the composition and settles to form a hard cake. Then, although the composition is a single package coating-type composition, it is necessary to thoroughly stir the composition before application to redisperse the inorganic filler and make the composition homogeneous. A single package coating-type composition provides an advantage only when the composition can be applied without the need to stir the composition before application. If the composition requires stirring before application, there is no advantage to using a single package-type material, and any two package-type composition can be used.
Japanese Patent Publication No. SHO-59-5156 (referred to hereinafter as "Prior Art IV") discloses a composition containing an enamine, and Japanese Patent Publication No. HEI-5-8730 (referred to hereinafter as "Prior Art V") discloses a composition containing a ketimine, respectively. Both Prior Art IV and Prior Art V, however, incorporate standard inorganic fillers which, when stored over a long period, pose disadvantages such as settling of the inorganic filler and slow curing speed.
It also is known that an organic or an inorganic anti-settling agent can be used in conjunction with an inorganic filler to prevent the filler from settling. However, when a commonly-used anti-settling agent is mixed with an oxazolidine-isocyanate composition, the anti-settling agent can retard curing or adversely affect the storage stability of the composition.
The present invention is directed to overcoming the drawbacks and disadvantages of the prior art compositions. An important aspect of the present invention therefore is to provide moisture-curable urethane resin compositions that do not separate and settle in storage, that cure relatively quickly in air, and that do not produce blisters in the film.